In the Phase I program, an optically based instrument will be developed for in-situ monitoring of cell density in bioreactors used for manufacturing biopharmaceuticals. The cell density monitor employs a novel design integrating recent advances in opto-electronic technology to provide a monitor, which eliminates interference from both biofouling of exposed optical surfaces and aeration bubbles. Biofouling and bubbles present substantial problems in existing commercial cell density monitors. The in-situ probe design for the cell monitor will be compatible with steam sterilization. In the Phase I program, the cell density monitor will find commercial applications in improved process control for industrial bioreactors used for producing biopharmaceuticals and commodity chemicals. The monitor would lead to increased productivity for these industries. PROPOSED COMMERCIAL APPLICATION: The in-situ monitor would be utilized in monitoring cell density in industrial bioreactors used for production of biopharmaceuticals and commodity chemicals, including production, pilot, and research scale bioreactors.